This invention relates to an apparatus for forcing grease to desired points of lubrication within a mechanical device. The invention is particularly suitable for use in applications where a lubricant and a polyester plasticizer are injected under high pressures into a mechanical device or assembly, such as a valve assembly or a pump assembly.
Many mechanical devices require lubrication in various places within the assembly, especially to locations where significant friction may be encountered. Grease fittings have long been used in order to easily supply lubricant to these frictional points. A grease fitting is generally mounted on an outer surface of a mechanical assembly, and allows grease to "flow" under pressure from a reservoir through the fitting to the frictional points. In addition, grease fittings are generally intended to hold grease under pressure within the fitting and a passageway within the mechanical assembly from the fitting to the frictional points, so that grease will be automatically supplied to the intended places when required.
In recent years, it has become common to use grease not only for a lubricant, but also as the carrier of plastic particles designed to act as a sealer or a packing material. Pumps and valves typically have places between a rotational member and a stationary member where a packing is inserted. The packing material, such as Teflon.TM. or graphite impregnated asbestos, acts to some extent as a lubricant, but is principally intended to seal that area and make up dimensional variations between the rotational and stationary members. Since the packing material may tend to disintegrate during continued operation, it has been found necessary to repack pumps and valves on a regular basis. Rather than dismembering the assembly for repacking, it has been found acceptable in many applications to inject grease and a packing-type material to the desired area. Regular injection of the grease/packing material composition replenishes the packing in the assembly and offers an efficient technique for substantially reducing both equipment down time and maintenance costs.
The grease/packing material mixture typically has a consistency similar to the packing, and is generally highly viscous. It has therefore been necessary to inject this mixture under high pressures to cause "flow" to the desired locations. Since the mixture is preferably injected on a regular basis and one piece of equipment may have a plurality of places requiring a packing material, grease fittings have been employed to enable a hand gun or other mechanism to be easily attached to the fitting for injecting the mixture. The grease/packing material mixture is therefore injected under pressure from the gun through the fitting to the desired place within the assembly.
Some commercial high pressure grease fittings have a metallic ball which is acted upon by a spring to normally engage a seat and thus seal the grease within the fitting and the mechanical assembly. When a grease gun is attached to the fitting, the pressure of the injected grease unseats the ball and allows grease to enter the fitting and a passageway from the fitting to the desired place within the assembly. Movement of the ball away from the seat typically compresses the spring, and grease is allowed to flow between the ball and the internal walls of the fitting.
A problem has repeatedly been encountered with the use of conventional grease fittings and grease/packing material mixtures. The packing material particles may become lodged between the ball and the internal wall of the fitting, so that the fitting becomes "plugged" and further passage of the mixture is not possible. When a fitting becomes plugged, the pressure from the gun is often increased in an attempt to "clear" the fitting. The pressure within the fitting is often increased, however, to the extent that the fitting "blows out". During blow-out of a fitting, the high pressure build up in the fitting causes a spring retainer to give way, so that the ball and spring can be expelled from the fitting.
The possible detrimental effects of a plugged or blown-out fitting are numerous. Additional lubrication may not be injected through a plugged fitting, so that the packing may deteriorate, causing a leak. Alternatively, the surfaces in the area of the packing may become scoured or otherwise damaged because the packing is not being replaced. If the fitting blows out, the ball may not seat to hold the lubricant in the assembly. More serious, however, is the possibility that the spring, ball, or other portions of the fitting may be forced into the area of the packing and damage the equipment intended to be lubricated.
It is advantageous, at times, to provide a grease fitting wherein the ball seats with a plastic seal, rather than having a metal-to-metal seal. In commercial fittings, a plastic seal may be held in place by a sleeve which is thereafter secured in a fixed position.
An additional problem associated with conventional fittings is that the sleeve either presses against the plastic seal with too much force, so that the seal is damaged, or that the sleeve does not provide sufficient force to render the seal immovable. Either one of these conditions has a detrimental effect on the expected life of the seal, and it is a feature of this invention to prolong the life of a plastic seal within a grease fitting.
The instant invention provides a grease fitting particularly suitable for use in high pressure applications utilizing a mixture of a lubricant and a polyester plasticizer. The disadvantages of prior art grease fittings are overcome with the present invention, and an improved grease fitting is hereinafter provided.